DESCRIPTION (provided by investigator): The etiology of Attention Deficit Hyperactivity Disorder (ADHD) is poorly understood and identification of modifiable environmental risk factors is important for reducing its incidence. Manganese (Mn) is both an essential nutrient and, at high levels, a potential neurotoxicant to which the general population is commonly exposed. The primary aim of the proposed research is to investigate the association of prenatal Mn with behaviors associated with ADHD among infants using the Neonatal Behavioral Assessment Scale (NBAS), and among school-aged children (median=8 years) using three assessments: (1) clinically diagnosed ADHD;(2) behaviors associated with ADHD assessed with the Conners'Rating Scale for Teachers: and (3) behaviors associated with ADHD measured with formal psychometric tests, including the Neurobehavioral Evaluation System 2 Continuous Performance Test, and components of the Wechsler Intelligence Scale for Children-Third Edition. We will also investigate potential synergism between Mn and lead (Pb) on risk for ADHD. The study will be conducted among a birth cohort of 788 infants born between 1993 and 1998 to mothers residing adjacent to a metal- and PCB-contaminated harbor and Superfund site in New Bedford, Massachusetts. Mn is measured in archived cord blood samples. Associations will be estimated with multivariable regression, controlling for a wide range of covariates. The proposed study is the largest U.S. study to date to assess the effect of prenatal Mn on subsequent neurobehavior in children and will benefit from the use of a well characterized population whose development has been assessed longitudinally since birth and for whom a wealth of information on risk factors for adverse child development is available. Results will provide important insight into the role of Mn as a potentially remediable risk factor for common behavioral disorders such as ADHD. PUBLIC HEALTH RELEVANCE: Manganese (Mn) is a naturally occurring metal which is both an essential nutrient, and potential neurotoxicant. This study will investigate the association between prenatal Mn and childhood neurobehavioral development, particularly ADHD-related behavior. Our findings will provide important insight into the role of Mn as potentially remediable risk factor for this increasingly common and costly behavioral disorder of childhood.